1. Field of the Invention
The present invention relates generally to transmission power control management, and particularly, to transmission power control management in a User Equipment (UE) of a High Speed Packet Access (HSPA) network.
2. Description of the Related Art
As per the technical specification of the 3rd Generation Partnership Project (3GPP) (3GPP TS 25.214 V07.04.00 and section 5.1.2.2.1), when an UpLink Discontinuous Transmission mode (UL_DTX_mode)=1, a Transmit Power Control (TPC) command does not have to be transmitted in any downlink slot starting during an uplink Dedicated Physical Control CHannel (DPCCH) slot, which is in an uplink DPCCH transmission gap, as defined in subclause 6C.2. Accordingly, a network is not required to transmit TPC commands to a UE in Fraction Dedicated Physical CHannel (F-DPCH) slots, which start during a UL transmission gap. Also the specification provides that the UE shall ignore any TPC commands received in an F-DPCH slot starting during an uplink DPCCH slot, which is in an uplink DPCCH transmission gap, as defined in subclause 6C.2. Accordingly, a UE ignores TPC commands sent by the network that overlaps with the uplink transmission gap.
In case of an uplink DPCCH transmission gap, as defined in the specification, the UE adds together the values of TPC Commands (TPC_cmd) derived from each TPC command combining period in which a TPC command is known to be present and is not ignored, as described above, and which cannot be applied before the uplink DPCCH transmission gap. The UE then applies the resulting sum of TPC_cmd values, when the uplink DPCCH transmission resumes. Thus, the TPC command applied at the time of resumption of transmission is a logical sum of the TPC commands derived from each TPC combining period.
Also, as per the specification, when UL_DTX_mode=1, a TPC command does not have to be transmitted in any downlink slot starting during an uplink DPCCH slot, which is in an uplink DPCCH transmission gap.
FIG. 1 illustrates a conventional timing diagram in which a UL transmission resumes from a DTX/Discontinuous Reception (DTX/DRX) gap and ends after a brief period of transmission.
Referring to FIG. 1, TPC commands sent by the network and their subsequent interpretation by the UE, as per existing description of 25.214 07.04.00, are shown. Thus, as per 3GPP technical specification TS 25.214 V07.04.00, section 5.1.2.2.1 or 5.1.2.3 and release R1-071824, TPC commands received in F-DPCH at positions NOFF1=0 and 2 for slot number #4 101 do not have to be transmitted by the network, and should also be ignored by a UE, if received from the network.
However, because the output of γ equals 1, where γ denotes an output of the combined TPC commands, if the TPC commands from all the Radio Link Sets (RLSs) are reliably “1”, or the output of γ equals −1, if a TPC command from any of the RLSs is reliably “0”, the UE needs TPC commands of all the RLSs to derive a TPC command value as UP.
Consequently, power control transmission decision determined by the UE using methods of the prior art during DTX/DRX modes, as described above, is not efficiently handled. Further, because the prior art UE uses 2 DPCCH preambles prior to transmission of the actual data, the same power is used on both the DPCCH preambles at the time of resumption of transmission, which leads to sub optimal use of the available preambles.